‘Record-shattering’ heatwaves to become far more likely without urgent climate action, research warns

‘We need to prepare for more heat events that shatter previous record temperatures by large margins,’ study author tells The Independent

Daisy Dunne
Climate Correspondent
Monday 26 July 2021 16:01

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“Record-shattering” events similar to North America’s recent deadly heatwave could become far more likely in the coming years if little is done to tackle rapidly rising greenhouse gas emissions, a new study says.

During an unprecedented heatwave last month, several regions in the US and Canada experienced temperatures that were several degrees higher than any previous records.

The research finds that similar record-shattering heatwaves could become between two and seven times more likely across the world by 2050, when compared to the last three decades, if greenhouse gas emissions rise extremely quickly.

And such events could become up to 21 times more likely by 2080 if little is done to tackle rising emissions, the study says.

However, taking rapid action on greenhouse gas emissions could stem much of the expected increases in record-shattering heat, the scientists add.

The findings come just months before world leaders are due to meet for a major global climate summit in Glasgow. The talks are seen as crucial for getting the world on track to meeting its aspirational goal of limiting global heating to 1.5C above pre-industrial levels.

“We need to prepare for more record heat events that shatter previous record temperatures by large margins,” Dr Erich Fischer, a senior scientist at ETH Zurich and lead author of the study, published in the journal Nature Climate Change, told The Independent.

“This is yet another piece in the puzzle that demonstrates that, in order to reduce the risk of such record-shattering heat, greenhouse gas emissions need to be reduced very rapidly.”

Last month’s record-breaking North American heatwave stunned climate scientists.

The event saw Canada set a new temperature high of 49.6C (121F) – more than 4C above the previous record of 45C (113F). Parts of the US including Seattle and Portland also saw temperatures that were several degrees above previous records.

People rest at the Oregon Convention Center ‘cooling station’ during last month’s record heat

The new research uses climate models to assess how the probability of such “record-shattering” events occurring anywhere in the world is likely to change in the coming decades.

It considers “record-shattering” events to be week-long heat extremes that break previous records by at least two standard deviations.

The researchers looked at the probability of such events occurring under a range of future scenarios.

This included a future scenario where greenhouse gas emissions are extremely high (known as “RCP8.5”) and a scenario where temperature rise is successfully limited to well below 2C (known as “RCP2.6”). (Limiting global heating to well below 2C is the goal set by countries under the Paris Agreement.)

The research finds that, under a scenario of very high greenhouse gas emissions, week-long heat events that break records by three or more standard deviations will be come between two and seven times more likely in the period 2021-2050 and three to 21 times more likely in the period 2051-2080, when compared to the last three decades.

In the second half of the 21st century, record-shattering heat events could occur every six to 37 years somewhere in the northern midlatitudes, the research adds.

The “hotspot areas” for record-shattering heatwaves are likely to include densely populated areas such as the eastern US, central Europe, eastern Asia and parts of South America and Africa, the scientists say.

Though heatwaves will continue to get more extreme in the coming decades, rapid action to slash the rate of greenhouse gas emissions could prevent much of the expected increases in the second half of the 21st century, said Dr Fischer.

“If we are able to stabilise temperatures at 2C, we should expect to see less such record-shattering events after a couple of decades,” said Dr Fischer.

“The heatwaves would still be there but we would not expect them to break records by those margins.”

The new research shows that the world is likely to see more “unprecedented events” as the climate warms, said Dr Scott Power, a senior scientist at the Australian government’s Bureau of Meteorology, who was not involved in the research.

“The new study further highlights that reducing global greenhouse gas emissions can moderate the likelihood of record shattering,” he told The Independent.

“Unprecedented events like these could, in some instances, push ecosystems and societies beyond their ability to cope.

“Later this year nations from around the world will gather in Scotland to discuss cuts to greenhouse gas emissions. This new study provides further weight to an already compelling case that further cuts are required.”

Dr Vikki Thompson, a senior research associate at the University of Bristol, added that it is worth noting that the world currently has targets in place to avoid the very high greenhouse gas emissions expected under the RCP8.5 scenario.

“The good news is that we can prevent the worst case shown in this study – we are already on target to be below it and further reductions in emissions will reduce the risk of unprecedented extremes further,” she said.

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